MESA Electronic 4C27, Руководство пользователя, Страница: 10 / 32

CONFIGURATION
WATCHDOG ENABLE
The 4C27 has a hardware watchdog timer that will reset the CPU unless 'fed' periodically by
system software. In a DOS environment, the BIOS performs this service when it services the
hardware tic interrupt. When other operating systems are used, (Linux,PSOS,QNX etc.) it may be
necessary to disable the watchdog. Watchdog enable is controlled by jumper W5. When W5 is in the
up position, the watchdog is enabled. When W5 is in the down position, the watchdog is disabled.
LITHIUM CELL ENABLE
The 4C27 has Lithium coin cell that powers the clock/calendar and the CMOS setup storage
RAM. If jumper W5 is moved to the "down" position, the Lithium cell will be disconnected. The 4C27
may be shipped with the cell disconnected, so you may need to move W5 to the "up" position in order
to use the battery backed clock/calendar.
The 4C27 BIOS does not use the CMOS setup RAM, so it is possible to run the 4C27 with no
Lithium cell if desired.
FLASH BIOS
The 4C27 BIOS chip is a 5V flash memory device and can be reprogrammed in-place to update
the BIOS, or change from ROM-DOS to non ROM-DOS BIOS's. The program 4C27WBIO.EXE is
used to re-write the BIOS. The batch file ROMBIOS.BAT on the distribution disk shows the standard
4C27WBIO parameters. Contact MESA if you need any special code in the BIOS. If you supply us
with a standard 55-AA type external ROM image, we can add it to the BIOS image for you.
Make sure that you do not have a memory manager installed when you update the BIOS, or
you may corrupt the BIOS image. If this happens, you will need to get a new BIOS chip from
MESA.
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4C27 CPU USER'S MANUAL